Where can I go near Kansas City to get Subs and Amp installed? Also, what line

[Flamin_Heaters]

converter do I need? I have a 1998 Lincoln Navigator with the original stereo. I hear I need a Line In converter, and dunno exactly which one to get!

My Subs are 2 12' Rockford Fosgate P1's
My Amp is a Rockford P300